Inclined rolling facility, inclined rolling method, and method for manufacturing metal tube

Abstract

To provide an inclined rolling facility, an inclined rolling method, and a method for manufacturing a metal tube.SOLUTION: An inclined rolling facility of the present invention includes three rolling rolls arranged in an inclined manner on a circumference around a pass line, and respective guides arranged the circumference with the pass line as the center and among the three rolling rolls, where the guide has a suppressing portion that suppresses bulging of a material to be rolled, and the gap in the direction perpendicular to the pass line in the three rolling rolls and the guides satisfies a formula (1). 0≤Dg-Dr<35 ...(1)SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an inclined rolling facility for rolling a metal tube, an inclined rolling method, and a method for manufacturing a metal tube.

Background Art

[0002] Among the fields where seamless metal tube products are used, in fields where particularly excellent corrosion resistance and high strength are required, in order to improve the corrosion resistance performance, two-phase stainless steels (specifically equivalent to JIS G3459 SUS 329J1, 329J3L, 329J4L) and austenitic stainless steels (specifically equivalent to JIS G3459 SUS 301, 302, 304, 305, 309, 310, 312, 315, 316, 317, 836, 890, 321, 347) containing a large amount of alloying elements added to exhibit excellent corrosion resistance performance, and seamless tubes of Ni-based alloys (specifically equivalent to JIS H4552 NW4400, NW6007, NW0276, NW6022, NW6002) are used.

[0003] These steel types and alloys contain a large amount of alloying elements added to exhibit excellent corrosion resistance performance. Therefore, the structure is a single austenite phase or a multiphase structure containing an austenite phase. The austenite phase with a face-centered cubic lattice (fcc) structure often has a lower yield strength than the ferrite phase and martensite phase with a body-centered cubic lattice (bcc) structure under a use environment of about low temperature to normal temperature. Therefore, when a higher yield strength is required for a material containing an austenite phase, cold working needs to be added, and high yield strength improvement using dislocation strengthening by processing is required. In addition, seamless tubes are threaded and may be used by connecting the tubes together with the threaded parts. In order to process the shape of the threaded part with high precision, it is necessary to have a high roundness of the cross-section of the metal tube. For such reasons, processing is required to achieve high yield strength improvement while maintaining high roundness.

[0004] For example, in high-strength and highly corrosion-resistant steel pipes with an outer diameter of 3-1 / 2 inches or more used for oil well pipes and the like, cold working such as cold drawing and cold pilgering is frequently used, and high-strength steel pipes with a yield strength of 125 ksi or more have been put into practical use (see Non-Patent Document 1).

[0005] The cold drawing process described in Non-Patent Document 1 is an effective method not only for improving the strength in the longitudinal direction of the steel pipe but also for equalizing the wall thickness distribution in the longitudinal direction of the steel pipe. However, before the drawing process, many processes are required, such as softening heat treatment of the steel pipe, pickling, chemical conversion treatment for applying a lubricating film, and pipe end processing for creating a gripping part during drawing. Also, from the perspective of limiting the pressure required for drawing and preventing seizure on the tool, the wall thickness reduction rate can only be about 20%. Furthermore, if the wall thickness reduction amount in one drawing process is insufficient, it is necessary to repeat the series of processes from the softening heat treatment again. Moreover, since the shape of the steel pipe after drawing is uniquely determined by the tool dimensions used for drawing, tool replacement is required when changing the size, which is not suitable for small-lot and multi-variety production. And because there are many processes required when performing the drawing process, there is a problem that the equipment investment and energy consumption also become large.

[0006] On the other hand, the cold pilgering process described in Non-Patent Document 1 does not require pre-treatment of the steel pipe and can obtain a high wall thickness reduction rate. However, the feed amount in one pass is as small as several tens of mm, resulting in poor production efficiency. There is also a problem that the shape of the rolling roll is complex and the tool manufacturing load (specifically, the work load and economic load for manufacturing the rolling roll) is large.

[0007] As a technology for solving these problems, for example, the technology of Patent Document 1 can be cited. In the technology of Patent Document 1, an inclined rolling mill having two or more rolling rolls whose rotating axes are arranged inclined with respect to the rolling pass direction center line of a metal tube (hereinafter, may also be referred to as "pass line") is used, and a cold rolling method is proposed in which a metal tube is passed through the roll gap of this inclined rolling mill for rolling. Thereby, surface coating application to the metal tube before processing, preprocessing such as tube end processing, etc. are not required, and the strength of the metal tube can be improved by cold working with high processing efficiency, and it is said that good effects can be obtained in environmental protection and industry. In addition, by making the inner surface freely deformable, it is possible to prevent the surface pressure generated on the tool from becoming excessive, and since no surface defects such as seizure generated in cold drawing occur and desired processing strain can be added, it is also suitable for small-lot production of multiple varieties.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Non-Patent Documents

[0009]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0010] As described above, the cold rolling method described in Patent Document 1 has various advantages. The tilting rolling mill used in the cold rolling method of this Patent Document 1 has two or more rolling rolls arranged obliquely with respect to the pass line. The tube to be rolled is passed through the roll gap of the tilting rolling mill to perform diameter reduction rolling to obtain a metal tube. However, during the diameter reduction rolling, a large stress is applied in the circumferential direction of the tube to be rolled by the rolling load from the rolling rolls, and excessive deformation may be applied to the tube to be rolled. Therefore, in the cold rolling method of Patent Document 1, as a technique for making the cross-sectional shape of the rolled metal tube closer to a perfect circle, that is, improving the roundness of the metal tube, it cannot be said that it is sufficient.

[0011] In addition, the provision of a technique for improving the roundness of the rolled metal tube is required not only for cold rolling but also for hot rolling and warm rolling.

[0012] The present invention has been made in view of the above problems, and an object thereof is to provide a tilting rolling facility, a tilting rolling method, and a method for manufacturing a metal tube capable of making the cross-sectional shape of the metal tube after tilting rolling closer to a perfect circle.

Means for Solving the Problems

[0013] In order to solve the above problems, the present inventors have intensively studied a tilting rolling method for improving the roundness of a metal tube and a method for manufacturing a metal tube using this tilting rolling method. In addition, intensive studies have also been conducted on a tilting rolling facility for realizing this tilting rolling method. Here, as an example, the study was conducted using a tilting rolling facility having three rolling rolls in which the rotation axes of the rolling rolls are arranged at an inclination angle with respect to the pass line.

[0014] As a result of the studies by the present inventors, it has been revealed that there is a method for making the cross-sectional shape of a metal tube after inclined rolling closer to a perfect circle. Specifically, a raw tube is supplied from the entrance side of the rolling rolls to the roll gap of the inclined rolling equipment, and while the raw tube is sandwiched between three rolling rolls, it is passed in the rolling pass direction (i.e., the advancing direction of the tube), thereby subjecting the raw tube to inclined rolling to obtain a metal tube of a predetermined dimension. During the inclined rolling of this raw tube, due to the rolling load in the circumferential direction of the tube from each rolling roll, the tube may be deformed into a shape in which the tube protrudes from between adjacent rolling rolls (see FIG. 8). At this time, the tube may be locally deformed by being bent with a large curvature by the rolling rolls, resulting in a decrease in the roundness of the metal tube. Therefore, it has been clarified that suppressing the deformation of the tube in the shape of protruding as described above is effective in improving the roundness of the metal tube.

[0015] And as a result of the studies by the present inventors, it has also been clarified that it is effective to appropriately arrange a guide for suppressing the protrusion of the tube that occurs during the inclined rolling of the raw tube between the rolling rolls of the inclined rolling equipment.

[0016] The present invention has been completed based on the above findings, and the gist thereof is as follows. [1] Three rolling rolls arranged inclinedly on the circumference centered on the pass line, and guides respectively arranged on the circumference centered on the pass line and between the three rolling rolls, wherein the guide has a suppressing portion for suppressing the protrusion of the tube to be rolled, and an inclined rolling equipment in which the gap in the direction perpendicular to the pass line in the three rolling rolls and the guide satisfies the formula (1). 0 ≦ D g -D r < 35 …(1) Here, D shown in the formula (1) r is the diameter (mm) of the circle centered on the pass line in contact with the three rolling rolls, and D g is the diameter (mm) of the circle centered on the pass line in contact with the guides arranged at three locations. [2] The inclined rolling equipment according to [1], wherein the axial distance L between the restraining portion of the guide and the rolling portion of the rolling roll satisfies the formula (2). -(D i ×0.80) ≦ L ≦ D i ×0.80 …(2) Here, D shown in the formula (2) i is the outer diameter (mm) of the tube to be rolled before rolling. [3] The inclined rolling equipment according to [1] or [2], wherein the cross-sectional shape of the guide perpendicular to the guide axis is any one of circular, polygonal, and arc-shaped. [4] The inclined rolling equipment according to any one of [1] to [3], wherein the inlet side surface angle of the guide and the inlet side surface angle of the rolling roll satisfy the formula (3). M g1 -M r1 ≧ 0.5 …(3) Here, M shown in the formula (3) g1 is the inlet side surface angle (°) of the guide, and M r1 is the inlet side surface angle (°) of the rolling roll. [5] An inclined rolling method using the inclined rolling equipment according to any one of [1] to [4], wherein when rolling while rotating the plain tube in the circumferential direction of the tube and advancing it in the axial direction of the tube, the overhang of the tube to be rolled between the rolling rolls is suppressed by the restraining portion of the guide. [6] A method for manufacturing a metal tube using the inclined rolling equipment according to any one of [1] to [4], having a rolling step of obtaining a metal tube by rolling a plain tube while rotating it in the circumferential direction of the tube and advancing it in the axial direction of the tube, and in the rolling step, the overhang of the tube to be rolled between the rolling rolls is suppressed by the restraining portion of the guide.

Advantages of the Invention

[0017] According to the present invention, it is possible to suppress deformation of a metal tube caused by the protrusion of the tube during inclined rolling. As a result, the cross-sectional shape of the metal tube after inclined rolling can be made closer to a perfect circle, so that improvement in the roundness of the metal tube can be realized.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0019] Embodiments of the present invention will be described with reference to the respective drawings. Note that the following description shows a preferred embodiment of the present invention, and the present invention is not limited to this embodiment.

[0020] 〔Inclined Rolling Equipment〕 The inclined rolling equipment of the present invention will be described with reference to FIGS. 1 to 6.

[0021] FIG. 1 is a schematic view showing an embodiment of the inclined rolling equipment of the present invention, and is a cross-sectional view at the center position of the equipment of the inclined rolling equipment viewed from the front. FIG. 2 is a schematic view for explaining a state in which rolling is performed on a pipe to be rolled using the inclined rolling equipment shown in FIG. 1, and is a view viewed from the front from the rolling outlet side. FIGS. 3 and 4 are views for explaining the rolling rolls of the inclined rolling equipment of the present invention. FIGS. 5 and 6 are views for explaining the guides of the inclined rolling equipment of the present invention. For easy understanding, in FIGS. 3(B), 4(B) and 5(A), the plain pipe 1 and the pipe to be rolled 2 are shown in cross section, and in FIGS. 3 to 5, some of the three rolling rolls 3, such as rolling rolls and guides, are omitted from the illustration.

[0022] The inclined rolling equipment of the present invention is one of the rolling equipment used in the manufacturing process of metal pipes. Hereinafter, as an example of the "rolling equipment", a cold rolling equipment for performing cold working on a material to be rolled will be described. For example, an inclined rolling equipment having three rolling rolls whose rotation axes are inclined with respect to the center line (pass line, that is, the pipe axis direction) of the rolling path of the plain pipe can be cited. Further, as an example of "rolling", the case of performing cold rolling will be described, but the present invention is applicable not only to cold rolling but also to hot rolling and warm rolling. Note that the "metal pipe" in the present invention refers to a seamless steel pipe, a welded steel pipe, a forged welded steel pipe, or a UOE pipe.

[0023] As shown in FIGS. 1 and 2, the inclined rolling equipment 10 of the present invention includes three rolling rolls 3 arranged obliquely on a circumference centered on the pass line 6, and on a circumference centered on the pass line 6 and between the three rolling rolls 3. And guides 4 respectively disposed therebetween. The plain pipe 1 is supplied from the rolling inlet side to the roll gap of the inclined rolling equipment 10, and the plain pipe 1 is passed in the rolling path direction (advancing direction) while being sandwiched by the three rolling rolls 3, whereby inclined rolling is performed on the pipe to be rolled 2, and a metal pipe can be obtained after rolling is completed (see FIG. 5(A)).

[0024] First, the rolling roll 3 will be described.

[0025] Figures 3(A) to 4(C) show diagrams for explaining the tilt angle β, crossing angle γ, and inlet surface angle M and outlet surface angle M of the rolling roll 3. Figures 3(A) and 4(A) are views of the pipe to be rolled and the rolling roll from above. Figures 3(B) and 4(B) are views of the pipe to be rolled and the rolling roll from the side. Figures 3(C) and 4(C) are enlarged views of the area b surrounded by the square frame in each of Figures (B), and only the rolling roll 3 is shown for explanation. r1 and the outlet surface angle M r2 As shown in Figures 2 to 4, etc., the rolling roll 3 is a roll for tilt-rolling the raw pipe 1 supplied to the tilt-rolling facility 10. The rolling roll 3 has a rolling part 3a, and the raw pipe is rolled by this rolling part 3a. The rolling roll 3 is arranged such that its rotation axis 7 is provided with a tilt angle β with respect to the pass line 6. The tilt angle β, as shown in Figures 3(A) and 4(A), when the rolling roll 3 is viewed from above (that is, in a direction perpendicular to the pipe axis direction and in the direction in which the rolling load is applied to the raw pipe 1), refers to the angle (unit: °) formed by the straight line in the pipe axis direction (pass line 6) and the rotation axis 7 of the rolling roll 3. The tilt angle β is not particularly defined. From the viewpoint of stably advancing the raw pipe 1 and the pipe to be rolled 2 in the advancing direction, it is preferable that the tilt angle β is in the range of 0.5 to 40.0°.

[0026] In addition to providing the tilt angle β, the rolling roll 3 may be arranged with a crossing angle (crossing angle) γ on the rolling outlet side. The crossing angle γ, as shown in Figures 3(B) and 4(B), when the rolling roll 3 is viewed from the side (that is, in a direction perpendicular to the pipe axis direction and perpendicular to the direction in which the rolling load is applied to the raw pipe 1), refers to the angle (unit: °) formed by the pass line 6 and the rotation axis 7 of the rolling roll 3. The crossing angle γ is not particularly defined. From the viewpoint of more appropriately controlling the rolling load on the raw pipe 1, it is preferable that the crossing angle γ is in the range of 0 to 45.0°.

[0027] Examples of the shape of the rolling roll 3 include a barrel-shaped roll and a conical roll. Figures 1 to 3, 5, and 6 show an example of a barrel-shaped roll, and Figure 4 shows an example of a conical roll.

[0028] Examples of the shape of the rolling roll 3 include a barrel-shaped roll and a conical roll. Figures 1 to 3, 5, and 6 show an example of a barrel-shaped roll, and Figure 4 shows an example of a conical roll.

[0029] When the shape of the rolling roll 3 is a barrel-shaped roll, the rolling roll 3 may be provided with an inlet side angle M of the rolling roll r1 and an outlet side angle M of the rolling roll r2 The inlet side angle M of the rolling roll r1 refers to the angle (unit: °) formed between the side surface of the rolling roll 3 on the inlet side of rolling (i.e., the tapered side surface of the rolling roll 3 whose cross-sectional shape gradually becomes smaller toward the inlet side of rolling) and a straight line 6a parallel to the tube axis direction (i.e., the pass line) when the rolling roll 3 is viewed from the side (that is, in a direction perpendicular to the tube axis direction and perpendicular to the direction in which the rolling load is applied to the raw tube 1), as shown in FIG. 3(C). Further, the outlet side angle M of the rolling roll r2 refers to the angle (unit: °) formed between the side surface of the rolling roll 3 on the outlet side of rolling (i.e., the tapered side surface of the rolling roll 3 whose cross-sectional shape gradually becomes smaller toward the outlet side of rolling) and a straight line 6a parallel to the tube axis direction (i.e., the pass line) when the rolling roll 3 is viewed from the side, as shown in FIG. 3(C). From the viewpoints of the bite property of the raw tube and the stability of the progress of the tube to be rolled, the inlet side angle M r1 is preferably set in the range of 0.2 to 10.0°, and the outlet side angle M r2 is preferably set in the range of 0.2 to 10.0°.

[0030] Even when the shape of the rolling roll 3 is a conical roll, as shown in FIG. 4(C), an inlet side angle M r1 and an outlet side angle M r2 may be provided. From the same viewpoints as described above, the inlet side angle M r1 is preferably set in the range of 0.2 to 10.0°, and the outlet side angle M r2 is preferably set in the range of 0.2 to 10.0°. Note that the definitions of the inlet side angle M r1 and the outlet side angle M r2 are the same as the description of the above barrel-shaped roll, so they are omitted.

[0031] Next, the guide 4 will be described.

[0032] Figures 5(A) and (B) show diagrams of the tube being rolled, and Figure 5(C) shows a diagram for explaining the inlet side angle M g1 and the outlet side angle M g2 of the guide. Figure 5(A) is a view of the tube being rolled and the guide as seen from the side, and Figures 5(B) and (C) are enlarged views of the area c enclosed by the square frame shown in Figure 5(A). Also, Figures 6(A) and (B) show diagrams for explaining an example of the cross-sectional shape of the restraining portion 4a of the guide.

[0033] The guide 4 has a restraining portion 4a that restrains the protrusion of the tube being rolled that occurs during inclined rolling. By using this guide 4, it is possible to prevent the deformation in which the tube (the tube being rolled) tries to protrude from between adjacent rolling rolls 3 during the inclined rolling of the raw tube 1 (see Figure 2). Since the present invention is a technique for preventing the roundness of the cross-sectional shape of the metal tube after inclined rolling (that is, the shape of the cross-section perpendicular to the tube axis direction) from deteriorating by effectively obtaining such an action, it is important to appropriately arrange the guide 4 between the rolling rolls 3.

[0034] Here, with reference to Figures 7 and 8, the roundness in the present invention and the reason for installing a guide between the rolling rolls will be explained respectively. Figure 7 shows an example of a cross-sectional shape perpendicular to the tube axis of the metal tube after inclined rolling, which is deformed into an elliptical shape. Figure 8 shows an example of a state in which inclined rolling is being performed on a raw tube using general inclined rolling equipment.

[0035] First, the roundness in the present invention will be explained.

[0036] In the cross-section perpendicular to the axial direction of the metal tube 23 shown in Fig. 7, when the maximum value of the outer diameter of the metal tube 23 (i.e., the major axis of the ellipse) is denoted as Dmax and the minimum value of the outer diameter (i.e., the minor axis of the ellipse) is denoted as Dmin, the difference between the maximum value and the minimum value of the outer diameter in the cross-section perpendicular to the axial direction of the metal tube 23, which represents the difference between the two (Dmax - Dmin), is denoted as C. The smaller the value of the difference (C) between the maximum value and the minimum value of the outer diameter, the better the roundness. Therefore, in the present invention, it is targeted that the value of C in the metal tube after rolling is 1.2% or less of the maximum value Dmax of the outer diameter, and the case where the value of C is within the above numerical range is defined as "good roundness".

[0037] Note that the outer diameter of the metal tube (unit: mm) can be measured using, for example, calipers. When measuring the outer diameter of the tube end, a scale may be used.

[0038] Also, when measuring the outer diameter at locations other than the tube end, the metal tube is cut perpendicular to the axial direction at the measurement location, and the shape of the cut surface is measured. In the present invention, the above maximum value and minimum value of the outer diameter are obtained by measuring the outer diameter of the tube at 24 equally spaced points in the circumferential direction of the tube on the cut surface, taking the maximum value among them as Dmax and the minimum value as Dmin. When measuring the outer diameter using calipers or a scale, in the cross-section perpendicular to the axial direction of the tube, the distance in the circumferential direction between two points that become the measurement positions on the tube circumference (i.e., the installation positions of the calipers or the scale) is set to be half of the tube circumference.

[0039] Also, the measurement position in the axial direction of the metal tube can be anywhere, but since non-steady part deformation is likely to occur in the regions including the head and tail ends of the metal tube, it is desirable to measure the outer diameter at locations excluding 20 mm from each of the head and tail ends, and more preferably at locations excluding 40 mm from each of the head and tail ends.

[0040] Next, the effects of installing a guide between the rolling rolls of the skew rolling equipment of the present invention will be described. As described above, through the study based on the experiments of the present inventors, it has been found that the difference (C) between the maximum outer diameter value and the minimum outer diameter value used for evaluating the roundness can be reduced by the guide installed between the rolling rolls.

[0041] The equipment shown in FIG. 8 is an example of a general skew rolling equipment 20, and the guide of the present invention described above is not provided between the rolling rolls 22 of the skew rolling equipment 20. In addition, FIG. 8 shows a cross-sectional view at the center position of the rolling equipment when viewed from the front of the skew rolling equipment 20 from the rolling output side so that the cross-sectional shape of the pipe being processed can be understood. As shown in FIG. 8, during skew rolling, the pipe 21 to be rolled may be deformed in a shape that protrudes from between the rolling rolls 22. This is because circumferential bending is applied to the pipe 21 to be rolled in the region between the rolling rolls by the rolling load from the rolling rolls 22. It has been clarified by the study of the present inventors that when this protrusion of the pipe occurs and it is bent with a large curvature of the rolling rolls 22, the pipe may be locally deformed, and as a result, the roundness of the metal pipe obtained after rolling may decrease.

[0042] On the other hand, FIG. 2 shows a state in which skew rolling is being performed on the pipe 2 to be rolled using the skew rolling equipment 10 of the present invention. As described above, a guide 4 is installed between the rolling rolls 3 shown in FIG. 2. According to the skew rolling equipment 10 of the present invention, it can be seen that the protrusion of the pipe 2 to be rolled from between the rolling rolls 3 is suppressed by the guide 4. This is because the guide 4 has an effect of suppressing the circumferential bending applied to the pipe 2 to be rolled in the region between the rolling rolls due to the rolling load from the rolling rolls 3. Thereby, a decrease in roundness can be prevented.

[0043] Therefore, hereinafter, the installation location, shape, etc. of the guide 4 of the present invention that can effectively obtain the above effects will be specifically described.

[0044] First, the installation location of the guide 4 will be described.

[0045] As shown in FIGS. 1(A) and 1(B), consider a circle centered on the pass line 6 in contact with each rolling roll 3 and a circle centered on the pass line 6 in contact with each guide 4. FIG. 1(B) is an enlarged view of the area a shown in FIG. 1(A). Here, the diameter (D r )(unit: mm) of the circle in contact with each rolling roll 3 is referred to as the roll gap, and the diameter (D g )(unit: mm) of the circle in contact with each guide 4 is referred to as the guide gap. Note that the dotted circles shown in FIGS. 1(A) and 1(B) are the above-mentioned "circles (centered on the pass line) in contact with the rolling rolls", and the length indicated by the double arrows of the dotted line is the diameter (D r ) of the circle. Also, the dashed-dotted circle is the above-mentioned "circle (centered on the pass line) in contact with the guide", and the length indicated by the double arrows of the dashed-dotted line is the diameter (D g ) of the circle.

[0046] In the present invention, each guide 4 is installed between the rolling rolls 3 so that the gap (G) in the direction perpendicular to the pass line between the diameter of the circle in contact with the rolling roll 3 and the diameter of the circle in contact with the guide 4 satisfies a predetermined condition.

[0047] Specifically, the diameter D r of the circle in contact with the three rolling rolls 3 and the diameter D g of the circle in contact with the guide 4 are installed for the rolling roll 3 and the guide 4 respectively so as to satisfy the formula (1). 0 ≦ D g -D r < 35 …(1)

[0048] The reason for defining the formula (1) is as follows. From the viewpoint of installing the guide so as not to hinder the progress of the raw tube 1 and the tube to be rolled 2, the diameter D g (that is, the guide gap) of the circle in contact with the guide 4 is set to be 0 mm or more larger than the diameter D r (that is, the roll gap) of the circle in contact with the rolling roll 3. That is, D g ≧D ris related to this. When the gap of the guide is smaller than the gap of the rolling roll, the guide 4 may hinder the progress of the pipe 2 to be rolled, and as a result, the pipe 2 to be rolled may stop. In addition, strong contact between the guide 4 and the pipe 2 to be rolled may cause scratches or seizure. Furthermore, the roundness may decrease due to the stress generated by unnecessary contact between the guide 4 and the pipe 2 to be rolled. The diameter D g is the diameter D r should be 0.2 mm or more larger than (that is, D g ≥D r +0.2 (mm)).

[0049] Also, in order to obtain the effect of suppressing the protrusion of the pipe 2 to be rolled during processing, the gap of the guide should be smaller than the gap of the rolling roll + 35 mm. That is, D g <D r +35 (mm) is related. When the gap of the guide is D r +35 (mm) or more, it is impossible to suppress the circumferential bending applied to the pipe 2 to be rolled in the region between the rolling rolls by the rolling load from the rolling roll 3, and as a result, the roundness deteriorates. The diameter D g is the diameter D r +30 (mm) or less (that is, D g ≤D r +30 (mm)). In addition, as shown in Fig. 1(B), the gap (G) in the direction perpendicular to the pass line in the three rolling rolls 3 and the guide 4 is the total value of the gaps provided on both ends with respect to the pass line 6.

[0050] The inclined rolling equipment 10 can obtain the operation and effect of the present invention by satisfying the above-described configuration and the formula (1). In addition, in order to further improve the operation and effect, it is also effective to satisfy the following relational expression.

[0051] In the guide 4 of the present invention, it is desirable to arrange the suppression part 4a in the vicinity of the rolling part 3a of the rolling roll 3. Explaining using the example shown in Fig. 5(A), the part where the diameter of the axial cross-section of the guide 4 is the largest is the suppression part 4a. It is desirable that the suppression part 4a is at a position close to the rolling part 3a of the rolling roll 3 in the axial direction of the guide 4. In the present invention, the region in the vicinity of the rolling part 3a suitable for installing this guide is defined as the guide installation region (R g )

[0052] The guide installation region (R g ) is, as shown in Fig. 5(B), a region composed of a predetermined range on the rolling-in side in the guide axis direction and a predetermined range on the rolling-out side in the guide axis direction from the intersection point y of the straight line x parallel to the guide axis and the rolling part 3a, when the intersection point y is used as a reference. The "predetermined range" means, when the outer diameter of the raw pipe 1 (that is, the material to be rolled before rolling starts) is D i , the range up to the position where it becomes 80% of D i (that is, D i ×0.8) from the intersection point y. The reason is as follows. The guide 4 needs to be installed at a position where the protrusion of the pipe to be rolled 2 is likely to occur. As a result of the study by the present inventors, it was found that there is a relationship with the outer diameter (D i ) of the raw pipe 1 at the position where the protrusion of the pipe to be rolled 2 is likely to occur. Furthermore, as a result of the study by the present inventors, it was found that the protrusion of the pipe to be rolled 2 can be effectively prevented by setting it within the range of "D i ×0.8".

[0053] This guide installation region can be represented by a position coordinate range. When the straight line x is regarded as the X-axis and the intersection point y is regarded as the origin, the rolling-in side becomes the negative side and the rolling-out side becomes the positive side. That is, the guide installation region (R g ) is a region in the guide axis direction that is not less than (-D i ×0.8) mm and not more than (D i ×0.8) mm.

[0054] In the present invention, the suppression part 4a of the guide is within the above-mentioned guide installation region (R g) is preferably arranged to be located within the range. Specifically, when the guide axis direction distance between the suppression part 4a of the guide 4 and the rolling part 3a of the rolling roll 3 is L, it is preferable that the L satisfies the formula (2). -(D i ×0.80) ≦ L ≦ D i ×0.80 …(2) Here, L shown in the formula (2) is the guide axis direction distance (mm) between the suppression part 4a and the rolling part 3a, and D i is the outer diameter (mm) of the tube to be rolled before the start of rolling.

[0055] The above-mentioned "predetermined range" is changed from the "range from the intersection point y to the position where it becomes 80% of D i (that is, D i ×0.8) " described in the above description to the "range from the intersection point y to the position where it becomes 50% of D i (that is, D i ×0.5) ". In this case, the position coordinate range of the guide installation area (R g ) is a range of (-D i ×0.5) mm or more and (D i ×0.5) mm or less in the guide axis direction.

[0056] It is more preferable that the suppression part 4a of the guide is arranged so that the guide axis direction distance L becomes 0 mm.

[0057] Next, the number of guides to be installed will be described.

[0058] In FIGS. 1, 2 and 5, as an example, an inclined rolling facility 10 is shown in which three guides 4 having a circular cross-sectional shape are installed between each rolling roll 3. Note that the inclined rolling facility 10 is not limited to this form, and the guide 4 of the present invention may be arranged one by one, or two by two, or four or more between each rolling roll 3. The number of guides 4 installed between each rolling roll 3 can be appropriately selected within the range of 1 to 10 in consideration of the interval between adjacent rolling rolls 3 and the rolling roll 3.

[0059] Next, the cross-sectional shape of the guide will be described.

[0060] The cross-sectional shape of the guide 4 of the present invention is not limited to circular. This "cross-sectional shape of the guide" refers to the cross-sectional shape perpendicular to the guide axis in the restraining portion 4a of the guide 4. The guide 4 of the present invention may have a shape that is easy to install between the rolling rolls 3. Examples of the cross-sectional shape of the guide 4 other than circular include polygons and arcs.

[0061] For example, when the cross-sectional shape is circular, as shown in the example of FIG. 5(A), when the guide 4 is viewed from the side, there are two conical shapes in contact with each other at the bottom surfaces of the conical shapes, and the cross-section in the guide axis direction is a rhombus. In the case of this example, the bottom surface portion of the conical shape becomes the restraining portion 4a. Although not shown, instead of the conical shape, an elliptical cone may be used, and a barrel-shaped guide may also be used.

[0062] Also, for example, when the cross-sectional shape is a polygon, as shown in the example of FIG. 6(A), when the guide 4 is viewed from the front, the cross-section perpendicular to the guide axis is a quadrilateral, and when the guide 4 is viewed from the side, the cross-section in the guide axis direction is also a quadrilateral. In the case of this example, it will be in contact with the metal tube over the entire length of the rectangular parallelepiped.

[0063] Also, for example, when the cross-sectional shape is an arc, as shown in the example of FIG. 6(B), it includes a side formed by an arc with a radius of D g / 2 in the cross-sectional shape, and a shape having a structure in which the side is in contact with the metal tube. That is, the arc includes not only a shape in which the cross-sectional shape is an arc, but also a shape having an arc in a part of the cross-section as described above.

[0064] In the case of the guide 4 in the examples shown in FIGS. 6(A) and (B), it will be in contact with the metal tube over the entire length in the longitudinal direction of the guide. In this case, the "guide axis direction distance L between the restraining portion 4a and the rolling portion 3a" may be set as L, which is the guide axis direction distance between the portion where the distance from the pass line is the smallest in the longitudinal direction of the guide 4 and the rolling portion 3a.

[0065] Next, with reference to FIG. 5(C), the surface angle of the guide will be described.

[0066] FIG. 5(C) is a side view showing an enlarged part of the region c surrounded by the square frame in FIG. 5(A), and only the guide 4 is shown for explanation. As shown in FIG. 5(C), the guide 4 may be provided with an inlet surface angle and an outlet surface angle. When the guide 4 is provided with an inlet surface angle and an outlet surface angle, in order not to hinder the progress of the raw tube 1 and the tube to be rolled 2, the inlet surface angle M of the guide 4 g1 is made more than 0.5° larger than the inlet surface angle M of the rolling roll 3 r1 That is, it is preferable to satisfy the following formula (3). M g1 -M r1 ≧ 0.5 …(3) Here, M shown in formula (3) g1 is the inlet surface angle of the guide, and M r1 is the inlet surface angle of the rolling roll.

[0067] By controlling the inlet surface angle M of the guide 4 so as to satisfy formula (3), it is possible to prevent the tube to be rolled from being bent in the circumferential direction. As a result, it is possible to prevent the raw tube 1 or the tube to be rolled 2 from coming into contact with the guide 4 at unnecessary locations, and it is also possible to prevent the roundness of the metal tube obtained by the stress generated by unnecessary contact from decreasing. The inlet surface angle M of the guide 4 g1 is made more than 1.0° larger than the inlet surface angle M of the rolling roll 3 g1 That is, it is more preferable that the relationship is M r1 -M g1 -M r1 ≧ 1.0.

[0068] The upper limit of the inlet surface angle M of the guide 4 g1 is not particularly defined. From the viewpoint of obtaining the effect of preventing the tube from protruding between adjacent rolling rolls 3, the inlet surface angle M of the guide 4 g1 is in relation to the inlet surface angle M of the rolling roll 3 r1 such that 3 ≧ M g1 -M r1It is preferably set as such.

[0069] In addition, for the same reason as the inlet side surface angle of the guide 4, the outlet side surface angle M of the guide 4 g2 is preferably 0° or more, and more preferably 1° or more. Also, the outlet side surface angle M of the guide 4 g2 is preferably 10° or less.

[0070] The inlet side surface angle M of the above-described guide g1 refers to the angle formed between the side surface of the guide 4 on the rolling inlet side with respect to the traveling direction of the pipe (that is, the tapered side surface of the guide 4 whose cross-sectional shape gradually becomes smaller toward the rolling inlet side) and a straight line 6a parallel to the pipe axis direction (that is, the pass line 6), as shown in FIG. 5(C). Also, the outlet side surface angle M of the guide g2 refers to the angle formed between the side surface of the guide 4 on the rolling outlet side with respect to the traveling direction of the pipe (that is, the tapered side surface of the guide 4 whose cross-sectional shape gradually becomes smaller toward the rolling outlet side) and a straight line 6a parallel to the pipe axis direction (that is, the pass line 6).

[0071] 〔Inclined rolling method〕 Hereinafter, an inclined rolling method for a metal pipe using the above-described inclined rolling equipment of the present invention will be described. Note that the description of the rolling rolls and the guide is omitted because it has already been given in the description of the inclined rolling equipment.

[0072] In the inclined rolling method of the present invention, as shown in FIGS. 1 to 6, rolling of a raw pipe is performed using an inclined rolling equipment 10 including three rolling rolls 3 whose rotation axes 7 are arranged with an inclination angle β with respect to the pass line 6 (pipe axis direction), and a guide 4 arranged between the three rolling rolls. Note that the rolling rolls 3 may be further arranged with a crossing angle γ.

[0073] The raw tube 1 is supplied to the roll gap of the inclined rolling equipment 10 from the inlet side of the inclined rolling equipment 10 (i.e., the right side of the paper shown in Fig. 5(A)). While sandwiching the raw tube 1 with the three rolling rolls 3, the raw tube 1 is passed in the rolling pass direction (the advancing direction shown in Fig. 5(A), etc.), thereby performing inclined rolling on the tube to be rolled 2. As a result, a metal tube having an outer diameter dimension reduced to a desired value can be obtained. In this example, a cold-rolled tube can be obtained.

[0074] In the inclined rolling method of the present invention, when the raw tube 1 is inclinedly rolled while being rotated in the circumferential direction of the tube and advanced in the axial direction of the tube, the overhang of the tube to be rolled 2 between the rolling rolls 3 is suppressed by the restraining portion 4a of the guide 4 installed between the rolling rolls 3.

[0075] As described above, the rolling roll 3 of the present invention is arranged with an inclination angle β. With such an inclined arrangement, the rolling roll 3 that rotates about the rotation axis of the rolling roll 3 utilizes the frictional force generated by the contact between the rolling roll 3 and the raw tube 1 to draw the raw tube 1 supplied to the roll gap in the rolling pass direction. Therefore, the raw tube 1 is rolled in a spiral shape while being rotated by the rolling roll 3. That is, the raw tube 1 is rolled while rotating in the circumferential direction of the tube and advancing in the axial direction of the tube.

[0076] Such a rolling form can be realized by making the roll gap of the rolling roll 3 smaller than the outer diameter of the raw tube 1 and arranging each of the rolling rolls 3 inclined as described above. Further, in this rolling form, the overhang of the tube to be rolled 2 in the region between the rolling rolls 3 is suppressed by the guide 4 installed between the rolling rolls 3, so that a decrease in the roundness of the cross-sectional shape of the rolled metal tube can be prevented.

[0077] As described above, according to the inclined rolling method of the present invention, in particular, pretreatment such as surface coating application or end processing of the raw tube before inclined rolling is not required. Also, while realizing an improvement in the hardness of the metal tube by inclined rolling, it is possible to suppress a decrease in the roundness of the cross-sectional shape after inclined rolling.

[0078] 〔Method for manufacturing metal tube〕 The following describes a method for manufacturing a metal tube using the inclined rolling equipment of the present invention described above. That is, in the manufacturing method of the present invention, the tube to be rolled is subjected to inclined rolling by the above-described inclined rolling method to obtain a metal tube.

[0079] The method for manufacturing a metal tube of the present invention has a rolling step of obtaining a metal tube by performing inclined rolling while rotating the plain tube 1 in the circumferential direction of the tube and advancing it in the axial direction of the tube. In this rolling step, the overhang of the tube 2 to be rolled between the rolling rolls 3 is suppressed by the restraining portion 4a of the guide 4 installed between the rolling rolls 3 (see FIGS. 1 to 6). By performing this rolling step, the resulting metal tube can suppress a decrease in the roundness of the cross-sectional shape after rolling.

[0080] In the method for manufacturing a metal tube of the present invention, for example, heat treatment may be performed on the metal tube after the above rolling step. Also, for example, the metal tube after the above rolling step may be pickled to remove the scale on the surface of the metal tube. The conditions for heat treatment and pickling treatment may be appropriately set according to the composition of the metal tube and the like.

[0081] In the present invention, the manufacturing conditions of the plain tube before performing the above rolling step are not particularly limited, and generally known manufacturing conditions can be adopted. Also, the plain tube before performing the rolling step is not particularly limited, and may be, for example, a hollow pipe material.

[0082] Also, even if there is a difference between the maximum outer diameter value and the minimum outer diameter value in the shape of the plain tube before performing the rolling step, the above-described effects of the present invention can be obtained. From the viewpoint of more effectively obtaining the effects of the present invention, the plain tube before performing the rolling step has an elliptical or circular cross-section perpendicular to the axial direction of the tube, and the value obtained by dividing the difference between the maximum outer diameter value and the minimum outer diameter value by the maximum outer diameter value (that is, ((maximum outer diameter value - minimum outer diameter value) / maximum outer diameter value)×100) is preferably 10% or less. More preferably, the value is 7% or less.

[0083] Note that the method for measuring the maximum and minimum outer diameters of the raw pipe before performing the rolling process shall be the same as the method for measuring the maximum and minimum outer diameters of the metal pipe described above.

Example

[0084] Hereinafter, examples of the present invention will be described.

[0085] A raw pipe with an outer diameter (D i ): 100 mm (difference between the maximum and minimum outer diameters: 0 mm), wall thickness: 5 mm, and length: 250 mm was taken from a stainless steel bar (material: SUS329J3L) conforming to JIS G 4303:2012 standard by machining. The raw pipe was subjected to inclined rolling using the above-described inclined rolling equipment and inclined rolling method of the present invention.

[0086] Note that, as shown in FIG. 2 etc., three guides 4 were installed between each pair of rolling rolls 3 in this inclined rolling equipment. The cross-sectional shape perpendicular to the guide axis of the guide 4 was the shape shown in Table 1. However, the inclined rolling equipment used for the inclined rolling of Pipe No. 1 was an equipment that did not provide any of the guides 4 of the present invention between the rolling rolls 3, as shown in FIG. 8.

[0087] The inclined rolling equipment used in this example was a cold rolling equipment. This inclined rolling equipment was a three-roll type inclined rolling mill having a barrel-shaped roll (rolling roll 3) with an inlet side surface angle M r1 of 3.5° and an outlet side surface angle M r2 of 4.0°. During rolling, the inclination angle β of the rolling roll 3 was 3° and the crossing angle γ was 0°, and the gap D r of the rolling roll 3 was set to 85 mm. Also, the inlet side surface angle M g1 and the outlet side surface angle M g2 of the guide 4, and the gap D g of the guide 4 were the respective values shown in Table 1. The restraining portion 4a of the guide 4 was installed such that the axial distance L in the pipe direction on the rolling inlet side between the restraining portion 4a and the rolling portion 3a of the rolling roll 3 was the value shown in Table 1.

[0088] Using this inclined rolling equipment, the raw pipe at room temperature was rolled in one pass.

[0089] Using the rolled metal tube, the roundness was evaluated. In this example, the above-mentioned metal tube refers to a cold-rolled tube. A caliper was used to measure the outer diameter, and the outer diameter was measured by the above-mentioned method. From the maximum outer diameter value Dmax and the minimum outer diameter value Dmin obtained by measuring 24 points at equal intervals in the circumferential direction of the outer diameter, the value of C representing the difference between the two (that is, C = Dmax - Dmin (unit: mm)) was calculated. The ratio of C to the maximum outer diameter value Dmax (that is, C / Dmax (unit: %)) is shown in Table 1. In this example, when the value of C / Dmax is 1.2% or less, it is evaluated as "qualified (that is, good roundness)". In the evaluation result column of Table 1, when the value of C / Dmax is 0.0% or more and 1.0% or less, the symbol "◎" is marked, and when it is greater than 1.0% and 1.2% or less, the symbol "○" is marked. On the other hand, when the value of C / Dmax exceeds 1.2%, it is evaluated as "unqualified", and the symbol "×" is marked in the evaluation result column of Table 1. Note that the measurement position in the axial direction of the tube was the central position of the metal tube (that is, the position corresponding to half of the total length of the tube).

[0090]

Table 1

[0091] As shown in Table 1, in the example of the present invention, the evaluation result of roundness was within the range of 1.2% or less, and the target value was also achieved. On the other hand, in the comparative example, the evaluation result of roundness was in the range of 1.4 to 3.6%, and the above target value could not be achieved. In particular, for Tube No. 1, since it was a tilt rolling facility without a guide, the value of C / Dmax was larger compared to the case of using the tilt rolling facility of the present invention. From the above, it was found that according to the present invention, a decrease in roundness can be suppressed.

Explanation of Reference Signs

[0092] 1 Plain tube 2 Tube to be rolled 3 Rolling roll 3a Rolling part 4 Guide 4a Suppression part 6 Pass line Rotation axis of the 7 rolling rolls 10 Inclined rolling equipment 20 Inclined rolling equipment 21 Tube to be rolled 22 Rolling roll 23 Metal tube D r Roll gap D g Guide gap β Inclination angle γ Crossing angle M r1 Inlet side angle of the roll M r2 Outlet side angle of the roll M g1 Inlet side angle of the guide M g2 Outlet side angle of the guide Dmax Maximum outer diameter value Dmin Minimum outer diameter value

Claims

1. Three rolling rolls disposed obliquely on the circumference centered on the pass line, Guides respectively disposed on the circumference centered on the pass line and between the three rolling rolls, The guide has a restraining portion for restraining the protrusion of the tube to be rolled, An inclined rolling facility in which the gap in the direction perpendicular to the pass line in the three rolling rolls and the guide satisfies the formula (1). 0 ≤ D ｇ -D ｒ < 35 …(1) Here, D shown in formula (1) ｒ is the diameter (mm) of a circle centered on the pass line in contact with the three rolling rolls, and D ｇ is the diameter (mm) of a circle centered on the pass line in contact with the guides arranged at three locations.

2. The inclined rolling facility according to claim 1, wherein the axial distance L between the restraining portion of the guide and the rolling portion of the rolling roll satisfies the formula (2). -(D ｉ ×0.80) ≤ L ≤ D ｉ ×0.80 …(2) Here, D shown by formula (2) ｉ is the outer diameter (mm) of the tube to be rolled before rolling.

3. The inclined rolling facility according to claim 1, wherein the cross-sectional shape perpendicular to the guide axis is any one of circular, polygonal, and arc-shaped.

4. The inclined rolling facility according to claim 2, wherein the cross-sectional shape perpendicular to the guide axis is any one of circular, polygonal, and arc-shaped.

5. The inclined rolling facility according to claim 1, wherein the inlet side surface angle of the guide and the inlet side surface angle of the rolling roll satisfy the formula (3). M ｇ１ -M ｒ１ ≥ 0.5 …(3) Here, M shown by formula (3) ｇ１ is the entrance side surface angle (°) of the guide, and M ｒ１ is the entrance side surface angle (°) of the rolling roll.

6. The inclined rolling facility according to claim 2, wherein the inlet side surface angle of the guide and the inlet side surface angle of the rolling roll satisfy the formula (3). M ｇ１ -M ｒ１ ≥ 0.5 …(3) Here, M shown in formula (3) ｇ１ is the inlet surface angle (°) of the guide, and M ｒ１ is the inlet surface angle (°) of the rolling roll.

7. The inclined rolling facility according to claim 3, wherein the inlet side surface angle of the guide and the inlet side surface angle of the rolling roll satisfy the formula (3). M ｇ１ -M ｒ１ ≥ 0.5 …(3) Here, M shown by formula (3) ｇ１ is the inlet surface angle (°) of the guide, and M ｒ１ is the inlet surface angle (°) of the rolling roll.

8. The inclined rolling facility according to claim 4, wherein the inlet side surface angle of the guide and the inlet side surface angle of the rolling roll satisfy the formula (3). M ｇ１ -M ｒ１ ≥ 0.5 …(3) Here, M shown by formula (3) ｇ１ is the entrance side surface angle (°) of the guide, and M ｒ１ is the entrance side surface angle (°) of the rolling roll.

9. An inclined rolling method using the inclined rolling facility according to any one of claims 1 to 8, When rolling while rotating the raw tube in the circumferential direction of the tube and advancing it in the axial direction of the tube, An inclined rolling method in which the restraining portion of the guide restrains the protrusion of the tube to be rolled between the rolling rolls.

10. A method for manufacturing a metal tube using the inclined rolling facility according to any one of claims 1 to 8, Having a rolling step of obtaining a metal tube by rolling while rotating the raw tube in the circumferential direction of the tube and advancing it in the axial direction of the tube, In the rolling step, a method for manufacturing a metal tube in which the restraining portion of the guide restrains the protrusion of the tube to be rolled between the rolling rolls.

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